Complex Mechanical Metamaterials

The structural complexity of metamaterials is limitless, but in practice, most attention has focused on periodic architectures, leading to relatively simple features. Here we discuss structurally complex metamaterials, which exhibit spatially textured and sequential behavior. First, advanced applications in soft robotics, prosthetics and wearable technology involve spatially textured mechanical functionality, which requires aperiodic architectures. A naive implementation of structural complexity invariably leads to geometrical frustration, which prevents coherent operation and impedes functionality. Here we introduce a combinatorial approach that allows to design aperiodic, yet frustration-free, mechanical metamaterials, and discuss the physics of a textured 3D metamaterial, as well as a multi-shape origami-based metamaterial.
Second, ordered sequences of motions govern the morphological transitions of a wide variety of natural and man-made systems. We show how to design and create metamaterials that translate a global uniform compression into a precise multistep pathway of reconfigurations. There innovations open new avenues towards mechanical metamaterials with unusual order and machine-like functionalities.